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President Lincoln FM detector fix | Radioaficion Ham Radio

President Lincoln FM detector fix


CB Radio Mods President Lincoln FM detector fix

Some users  reported a bad  FM  signal detection on weaker  signals. This  is  also what  I  recognized  at  all my  3  Lincolns  I  owned  in  the past years.

The reason and the fix are simple.

The input of the FM detector stage is wired  from L104  through a serial resistor of 10k (R1 in the schematic) toward the FM detector IC. But the schematic says “1k” instead.

With 10k  the FM  input signal  is attenuated so strong,  that  the detection below S5 gets more and more worse. You hear more  FM-noise  than  the FM-signal  itself, meaning  the S/N ratio gets worse.

The fix is easy:

MORE....... in pdf

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